1. Field of the Invention
Embodiments of the present invention relate to a control system that is applied to a hybrid vehicle in which an internal combustion engine and a motor generator are provided on an input side of a transmission mechanism.
2. Description of Related Art
As a control system for a hybrid vehicle, a system that suppresses a fluctuation in engine torque that is generated during a gear shift operation of an automatic transmission by properly using control of a motor generator and control of an electronic throttle valve in accordance with a state of charge of a battery is known (Japanese Patent Application Publication No. 2000-83303 (JP 2000-83303 A)). Other than JP 2000-83303 A, as related art literature associated with the invention, Japanese Patent Application Publication No. 2012-240551 (JP 2012-240551 A), Japanese Patent Application Publication No. 2011-218945 (JP 2011-218945 A), and Japanese Patent Application Publication No. 2004-203218 (JP 2004-203218 A) are available.
The device in JP 2000-83303 A reduces the engine torque by reducing an intake air amount through the control of the electronic throttle valve. However, because the control of the electronic throttle valve is accompanied by a reduction in the intake air amount, fuel economy is degraded. In addition, because whether to permit the control of the motor generator is influenced by the state of charge of the battery, there is a possibility that the fluctuation in the engine torque cannot be suppressed sufficiently only by the control of the motor generator. For this reason, this control system uses both the control of the motor generator and the control of the electronic throttle valve in the case where a fluctuation width of the engine torque is large and thus the fluctuation in the engine torque cannot be suppressed only by the control of the motor generator.
With respect to internal combustion engines, both an internal combustion engine in which one combustion mode is maintained, but also an internal combustion engine in which a change of the combustion mode that is accompanied by a change of an air-fuel ratio is executed, are available. When the change of the combustion mode is executed, it is accompanied by the change of the air-fuel ratio. Thus, engine power fluctuates. In the case where such an internal combustion engine is mounted in a hybrid vehicle that is provided with a transmission mechanism, a fluctuation in output that is caused by the change of the combustion mode and a fluctuation in output that is caused by a gear shift operation of the transmission mechanism are possibly generated.
In the case where these fluctuations in the output are generated in time periods that are sufficiently separated from each other, these fluctuations can be alleviated individually by the control of the motor generator. However, in the case where a combustion mode change request and a gear shift request of the transmission mechanism of the internal combustion engine overlap, it is desired that execution time periods of the change of the combustion mode and the control of the motor generator are re-examined and, in this way, fluctuations in the output are suppressed as much as possible from becoming large within a range of input/output limit in which overcharging and overdischarging of the battery can be avoided.